A NEW APPROACH FOR DOCUMENTATION, CONSERVATION AND PRESERVATION OF THE MONOLITHIC STATUES IN SAN AGUSTÍN AS PILOT FOR OUTDOOR
CULTURAL HERITAGE DOCUMENTATION IN COLOMBIA
A. Estela
a,
, J. Hamacher
b a
Research Associate, ICANH Instituto Colombiano de Antropología e Historia, Calle 12 No. 2-41 Bogotá D.C., Colombia
– aestelahotmail.com
b
PhD Candidate, AEGIS-CEMA-INCAL, Université catholique de Louvain, Place Blaise Pascal, 1, Bte L3.03.13, B-1348, Louvain-la- Neuve, Belgium
– julian.hamachergmail.com
KEY WORDS: San Agustín, Mantis, Z+F, Outdoor Heritage, ICANH, Monolithic Statues, Post Processing ABSTRACT:
The
“Instituto Colombiano de Antropología e Historia” ICANH started a new conservation project for the “San Agustín Archaeological Park
” Huila, Colombia in 2013. The objectives of this project are the documentation, conservation, and preservation of the numerous monolithic statues mainly by integrating the use of new technologies 3D models. A first phase of the project has
been completed, resulting in three-dimensional models of 66 of the monolithic sculptures in San Agustín. The methodology developed in this first phase will show the way for other heritage sites in Colombia and for subsequent phases applied to the
archaeological park. The 3D data has been obtained using two types of data acquisition technology: the Mantis Vision F5 using infrared structured-light SL and a laser scanner based on the phase shift PS technology, the Z+F Imager 5010. The results show
that future phases need improvement in data acquisition. Mainly the data obtained with the hand held scanner shows many lacunae. This article presents the observations during data processing on the basis of one sculpture,
“Escultura 23”. In conclusion, this first phase showed where to improve for the succeeding ones, for instance the detail of the meshes need to be increased if the models are
to be used for detailed conservation and preservation purposes.
Corresponding author.
1. THE PROJECT
The open air archaeological park of “San Agustín” Huila, Colombia figures on the UNESCO’s World Heritage List since
1995. The area is home to numerous monolithic statues be
longing to funerary complexes that date back to the “Clásico Regiona
l” period 1st- 10th century AD. In February 2013, the ICANH started a new conservation programme for this
important heritage site including the use of the latest technologies of documentation. This project is intended as a
pilot project for the whole country by applying 3D technology in the field of conservation, preservation and documentation.
Creating three-dimensional models for outdoor heritage monuments is a total novelty in Colombia and to date even in
scientific literature similar projects concerning monolithic statues with this kind of approach are seldom. The methodology
developed in this first phase will show the way for other heritage sites in Colombia and it aims at showing the advantages of a
virtual three-dimensional approach to heritage. In this manner, the project is carried out in various phases and
so far only the first consisting in the data acquisition with the subsequent 3D modelling has been completed and gave birth to
the digital models of a total of 66 statues found in the so called
“Mesitas” A and B as well as in the “Bosque de las Estatuas” with an additional model of the “Fuente del Lavapatas”. The
next steps will be to demonstrate in how far the 3D models can be used for educational, conservation and preservation
purposes. For instance the digital models have already been showcased in during an exhibition in Bogota. More than
showing the digital models to a large public, we hope to be able to associate the models to conservational and archaeological
data in order to render research easier and increase the accessibility to the artefacts.
The implementation of new non-destructive technologies for the study of cultural heritage in countries like Colombia still faces
various difficulties today and progresses only slowly. One main factor is the lack of knowledge of those new technologies and
that only a few specialists could bring in their expertise for projects such as this in order to obtain satisfactory results.
Another factor is the lack of equipment for data acquisition. Only few companies, generally resellers of the most renowned
brands, have such equipment and offer to rent them with an operator who is not acquainted with scanning cultural heritage.
The planning and progress of this project has been highly influenced by both of the upper mentioned factors. The lack of
discussion about the data with experts, regarding many of the points addressed here below, would have greatly helped in
obtaining more conclusions and certainly better results.
2. USED EQUIPMENT
The 3D data has been obtained using two types of data acquisition technologies: the Mantis Vision F5 using infrared
structured-light SL and a laser scanner based on the phase shift PS technology, the Z+F Imager 5010. It is difficult to compare
them as they use a very different approach of acquiring 3D data. The Mantis can be used directly on the surface of an object and
should not be held further away than 1m. The Z+F has a minimal distance of 0.3m and could theoretically be used up to a
distance of about 183m losing then obviously much accuracy. The maximal acquisition speed for the Imager 5010 is defined at
about 1 million points per second whereas the F5 has a fix
ISPRS Technical Commission V Symposium, 23 – 25 June 2014, Riva del Garda, Italy
This contribution has been peer-reviewed. doi:10.5194isprsarchives-XL-5-225-2014
225
acquisition speed of 0.5 million points per second. For the Mantis, the accuracy at 1m is up to 0.5mm and for the Z+F up to
0.6mm at 10m. The photographs for the textures of the models have been taken
using a Canon EOS 40D using an EF 24-70 f:2.8 lens. For the geo-referencing of the statues, a GNSS receiver Javad
Triumph-1 has been employed which uses 216 channels and can receive different signals GPS, L1, L2, L2C Y L5, GLONAS L1
and L2. 1 So far, for the theoretical abilities of the equipment used, in
practical terms, a selection of sculptures has been scanned with both scanners in order to enable a comparison of the results.
However, the main part of the models has been obtained by using the Z+F Imager 5010. The Mantis has been used mostly
where the accessibility of the monuments was difficult due to vegetation or other static objects located close to the target to be
scanned. Indeed, those constraints made the use of the Z+F sometimes impossible. The minimal distance could not be
respected, thus leaving no choice but using the hand-held scanner to obtain results. Furthermore, the simple fact that all
scanned objects are located outdoor had a critical impact on lighting conditions simply because they could not be controlled.
In addition, some of the monuments are protected against weather conditions by roofs set up on simple pilasters which
obviously cast shadows. Some of the statues are even located under a baldachin like structure of massive stone. Indeed, the
choice of the two different scanning systems was based upon the above described location of the sculptures.
3. WORKFLOW
